Factor XIIIA

Formalin-fixed, paraffin embedded tissue block or cell block, or 1 unstained charged slide for each test requested plus 3-4 additional unstained slides cut at 4 microns. Adequate space on each slide for control tissue is required.

Factor XIIIa is a blood proenzyme (coagulation factor) that is present in platelets, megakaryocytes, and fibroblast-like mesenchymal or histiocytic cells. Factor XIIIa is a dermal dendritic cell marker that is most frequently used with CD34 to differentiate dermatofibroma from dermatofibrosarcoma protuberans.